Left 4 Dead 3 Confirmed During Valve Office Tour?

In an intriguing turn of events, a leak of Left 4 Dead 3's existence seems to have sprung directly from the source: Valve's Bellevue-based offices.

A keen-eyed Dota 2 player, touring the offices as part of The International 3 tournament, took a snap of an internal changelog that apparently lists both Left 4 Dead 3 and Source 2 as current projects. The below photo compliments a similar 'leak' via internal Valve documentation in June, although we have not verified the validity of either.